Cannot resize APFS partition - "The new size must be different than the existing size"

I have a 1TB SSD on macOS High Sierra 10.13.6 with the following APFS partitions:

$ diskutil list
/dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                 Apple_APFS Container disk2         300.0 GB   disk0s2
   3:                 Apple_APFS Container disk1         254.0 GB   disk0s3

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +254.0 GB   disk1
                             Physical Store disk0s3
   1:                APFS Volume macOS High Sierra       225.1 GB   disk1s1
   2:                APFS Volume Preboot                 23.9 MB    disk1s2
   3:                APFS Volume Recovery                519.5 MB   disk1s3
   4:                APFS Volume VM                      1.1 GB     disk1s4

/dev/disk2 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +300.0 GB   disk2
                             Physical Store disk0s2
   1:                APFS Volume macOS Mojave            241.4 GB   disk2s1
   2:                APFS Volume Preboot                 49.0 MB    disk2s2
   3:                APFS Volume Recovery                1.0 GB     disk2s3
   4:                APFS Volume VM                      20.5 KB    disk2s4

I would like to resize the macOS Higher Sierra partition highlighted above to ideally take up all the free space dynamically, which I tried to do using the command:

$ diskutil apfs resizeContainer /dev/disk1 0
Started APFS operation
Error: -69743: The new size must be different than the existing size

Trying to enlarge using a fixed size does not work either:

$ diskutil apfs resizeContainer /dev/disk1 500g
Started APFS operation
Aligning grow delta to 246'000'209'920 bytes and targeting a new physical store size of 499'999'997'952 bytes
Determined the maximum size for the targeted physical store of this APFS Container to be 253'999'788'032 bytes
Error: -69771: The target disk is too small for this operation

Neither Time Machine nor FileVault is enabled.

For me it looks like you need to resize the container first. So something like

$ diskutil apfs resizeContainer /dev/disk0s3 500g

should help to avoid the error message you get on your second try.

I've got not much knowledge about the diskutil, but as far as I know Apple software overall, this seems to be the step you are missing here.

This helped me:

1. repair (internal, disk0 - in your case)

   diskutil repairdisk disk0

2. resize (synthesized, disk1 - in your case with HS)

   diskutil apfs resizeContainer disk1 0

After repairdisk resizeContainer works with no errors.

As an educated guess after reading around, the likely reason that the High Sierra container could not be resized was that it was not contiguous with the free space.

I have now zeroed-out Mojave and cloned the contents of High Sierra to there, whereupon I can resize that partition to occupy the free space.

Problem solved.